Quantification of the β-Stabilizing Effect of the Dicarbonyl(η5-cyclopentadienyl)iron Group

✍ Scribed by Felix Dulich; Karl-Heinz Müller; Armin R. Ofial; Herbert Mayr

• Book ID: 102260218
• Publisher: John Wiley and Sons
• Year: 2005
• Tongue: German
• Weight: 272 KB
• Volume: 88
• Category: Article
• ISSN: 0018-019X
• DOI: 10.1002/hlca.200590137

✦ Synopsis

Abstract

Kinetic investigations of the reactions of (prop‐2‐enyl)dicarbonyl(cyclopentadienyl)iron complexes 1 with benzhydrylium ions 3, and of dicarbonyl(cyclopentadienyl)[(1,2‐η)propene]iron(II) tetrafluoroborate (9⋅BF~4~) with π‐nucleophiles have been performed to elucidate the magnitude of the β‐effect of the [(CO)~2~FeCp] group (Fp group). Introduction of the Fp group into the allylic position of propene and 2‐methylpropene increases the nucleophilicity of the π‐bonds by nine and six orders of magnitude, respectively, with the result that the allyl‐Fp complexes 1a (N=6.78) and 1b (N=8.45) are among the strongest neutral π‐nucleophiles. Replacement of one β‐H‐atom in the isopropyl cation by the Fp group reduces the electrophilicity by more than 20 orders of magnitude, so that 9^+^ ranks among the weakest cationic C‐electrophiles (E=−11.2).